540 ScHAEFF — On the Slugs of Ireland. 



about 30 mm. long in March, reach their maturity in the following autumn, and 

 I quite agree with Simroth (38), who fixes the limit of age in A. ater at one 

 year. 



In the month of March the portion of the back and mantle between the lateral 

 bands becomes darker, a condition which is well seen in figs. 11 and 12; and in 

 that case a narrow light stripe is left between the dark portion and the bands. 

 But in some cases the back darkens uniformly, producing forms which have been 

 described by Roebuck as var. bicolor (fig. 15). I have found a half -grown form at 

 Whitechurch, near Dublin, in which the back remained light, whilst the sides 

 darkened (fig. 16). Similar young forms of the var. bicolor have been described 

 by Simroth (38) from the shores of the Baltic, and it is remarkable that every 

 instance of their occurrence is in close proximity to the sea. The light sides in 

 these specimens remain light throughout life. At Raheny, near Dublin, where I 

 have collected extensively last September, fully 30 per cent, were black above 

 with yellow sides, the remainder being entirely black with olive margin of 

 foot. All these had fully-developed reproductive organs. At Howth, Mr. Red- 

 ding has taken them with brilliant orange sides (fig. 15). In both cases the 

 specimens were found almost within reach of high tide. Only in one instance 

 have I seen this variety further inland in several specimens which were kindly 

 given to me by Mr. A. G. More, from his garden at Rathmines. This lies fully 

 three miles from the sea, but it may be that they found their way to the gardens 

 with plants from the sea-side. 



This disposes of the A. ater from the East Coast of Ireland. On the West 

 Coast the same species forms a very remarkable variety, possibly owing to the 

 difference of the meteorological conditions. If we look at Scott's (37) latest report 

 on the variability of the temperature in the British Isles, we find that during fifteen 

 years in Valentia Island, the thermometer only descended below freezing point six 

 times. In summer, during the same period, it only once rose above 70° F. {— 21° C). 

 There is in fact probably no place in Europe where such an equable climate exists 

 as on the South-West Coast of Ireland. 



As a result of these favourable meteorological conditions, adult forms of A. ater 

 survive the winter, but apparently do not develop reproductive organs in that 

 period. I received a large box of specimens, 80 mm. long, from the Aran 

 Islands in November. Their body cavity was almost entirely filled with a huge 

 liver and intestines, whilst the generative organs were like those of an ordinary 

 half-grown specimen. Again, in May, I collected everywhere in the mainland of 

 Kerry, and on Valentia Island, numbers of specimens considerably larger than 

 our Dublin full-grown forms, but again with hardly a trace of any reproductive 

 organ. Among these an olive-coloured variety is very common, and also one of a 

 cinnamon-red ; neither of these is banded. Besides these, rich brown forms, like 



